Method of preparing a thin ceramic composition with two materials, the composition thus obtained and the constituent electrochemical cell and membrane

Abstract

There is disclosed a method for preparing a thin ceramic and/or metallic solid-state composition consisting of three phases: a material (A), a material (B) and pores. The concentration of each phase varies continuously from one face of the article to the other in a continuous and controlled gradient. The porous matrix of material (A) has a porosity gradient of 0% to about 80%, the pores being completely or partly filled with material (B). The concentration of material (B) in the article therefore varies from 80% to 0% of small thicknesses.

What is claimed is: 
     
       1. A solid-state electrolyte or mixed ionic/electronic conductor apparatus that comprises:
 a) a thin solid composition consisting of at least one component selected from the group consisting of ceramic and metallic material; and 
 b) a surface concentration consisting of at least one component selected from the group consisting of ceramic and metallic material; 
 wherein the metallic material in part a) is different from the metallic material in part b); 
 wherein said mixed ionic/electronic conductor forms a mixed ionic/electronic conducting ceramic membrane; 
 wherein said membrane comprises material (A) selected from the materials of the brown-millerite family of formula (III):
   [Mc 2-x Mc′ x ][Md 2-y Md′ y ]O 6-w   (III)
 
 wherein Mc is at least one metal selected from the group consisting of alkaline-earth metals; 
 wherein Mc′ is at least one metal selected from the group consisting of lanthanides and actinides; 
 wherein Md is selected from the group consisting of 3d transition metals, and group 13 metals; 
 wherein Md′ is selected from the group consisting of 3d transition metals, group 13 metals, lanthanides, and actinides; 
 wherein x and y are identical or different, and are in the range of about 0 about 2; 
 wherein w is such that the structure is electrically neutral; 
 wherein a dense phase with a controlled surface porosity gradient is supported by a material (B); 
 wherein said material (B) is at least one component selected from the group consisting of carbides, nitrides, aluminum silicates and their derivatives, calcium phosphates and their derivatives; and 
 wherein undoped ceramic oxides provide a porous support. 
 
 
     
     
       2. The apparatus according to  claim 1 , wherein said solid-state electrolyte forms an electrochemical cell. 
     
     
       3. The apparatus according to  claim 1 , wherein said Mc is selected from the group consisting of Mg, Ca, Sr and Ba. 
     
     
       4. The apparatus according to  claim 1 , wherein Mc′ is selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y. 
     
     
       5. The apparatus according to  claim 1 , wherein said undoped ceramic oxides are selected from the group consisting of ZrO 2  and CeO 2 . 
     
     
       6. The apparatus according to  claim 1 , wherein said material A is selected from at least one of the formulas in the group consisting of:
   a) [Mc 2-x La x ][Md 2-y Fe y ]O 6-w   (IIIa);
 
   b) [Sr 2-x La x ][Ga 2-y Md′ y ]O 6-w   (IIIb); and
 
   c) [Sr 2-x La x ][Ga 2-y Fe y ]O 6-w   (IIIc).
 
 
     
     
       7. The apparatus according to  claim 2 , wherein said apparatus further comprises applying a reforming catalyst to the external face of the dense phase of material (A). 
     
     
       8. The apparatus according to  claim 2 , wherein said solid-state electrolyte is utilized for at least one function selected from the group consisting of extracting oxygen from a gas mixture containing oxygen and analyzing the presence of oxygen in a gaseous atmosphere. 
     
     
       9. The apparatus according to  claim 2 , wherein said apparatus produces ultrapure oxygen by separating oxygen from air by ionic conduction through an electrochemical cell. 
     
     
       10. The apparatus according to  claim 1 , wherein said apparatus is utilized for producing thermal and electrical energy within a solid-state fuel cell, by the reaction of oxygen with hydrogen, and
 wherein said oxygen is obtained by separating it from air, and by ionic conduction through a ceramic membrane. 
 
     
     
       11. The apparatus according to  claim 1 , wherein said membrane is a catalytic membrane reactor that produces syngas by the catalytic reaction of natural gas. 
     
     
       12. The apparatus according to  claim 11 , wherein said reaction further comprises steam and oxygen, and
 wherein said oxygen is obtained by separating it from air, and by mixing ionic/electronic conduction through said membrane. 
 
     
     
       13. The apparatus according to  claim 1 , wherein said membrane synthesizes an organic compound from hydrocarbon-based molecules, comprising at least one oxidation step, catalytic, non-catalytic, using gaseous oxygen, and
 wherein said oxygen is obtained by separating it from air, by mixed ionic/electronic conduction through said membrane. 
 
     
     
       14. The apparatus according to  claim 1 , wherein said membrane is utilized for gases, liquids, ceramic-to-metal seals, biomaterials and sensors.